Time has 20 mockcats and Ims 8 Sim-cats(and more than 20 take home tests)
So if u take the first free Aim-cat then even if ur performance is bad they will give you near to 1k discount..(I had a rank of AIR:162 or so and 99.6+%ntile and dey gave me a discount of 2/3rd of fee) So do take time free mock-test.
Its better to take the test of the both the institutes as their approach is varied...
Time has a really tough DI,tougher than cat, while IMS the level of the toughness is similar to cat.. So u can be prepared for a normal and a very tough paper(who knws hw tough next year will be..) Also there will be a clash on only maximum 8 sundays,so even if u miss the test,u can take it someother time..)
Personally in my 3years of CAT preparation(05,06,07) i din find CL tests to be so usefull as Time or IMS test...this is a personal opinion..we can happily differ on that
Its better to take the tests of 2 institutes,the maximum u gonna lose is a coupla thousands,but its well worth it....
If you are enrolling only for one, atleast make sure to get the tests of other institutes from your friends and try the papers at home..